FOLR1 and ovarian carcinoma: Further immunohistochemistry (IHC) studies (Figure 1B–D) indicated low relative expression (compared to high FOLR1 expression in the ovarian carcinoma cell line, HeLa) of the FOLR1 target antigen in lung alveolar epithelial cells of cynomolgus lung tissue suggesting an adverse event largely driven by on-target toxicity.